Apparatus for making laminated pressed board

ABSTRACT

A plurality of layers of comminuted material are deposited on an endless conveyor belt, with the uppermost and lowermost layers being finer than the central layer or layers. The loosely coherent band thus formed is trimmed longitudinally and longitudinally subdivided into a plurality of mats which are fed into a chamber wherein at least one lamina is applied to the upper surface. This chamber is maintained dust-free by pumping filtered air into it so that it is under superatmospheric pressure. The stacked mat and lamina are then fed into a hot press where together they are compressed into a hard coherent laminated pressedboard.

United States Patent Hut: 1 *July 1, 1975 APPARATUS FOR MAKING LAMINATED 3,224,758 12/1965 Siempelkamp 425/455 3,367,823 2/1968 Clausen et al. 156/572 PRESSED BOARD 3,490,977 1/1970 Lincoln t i A t 156/382 Inventor'- Gerhard Hiilz. Suchteln. rmany 3,576,692 4/1971 Hutz 156/622 [73} Assignee: G. Siempelkamp & Co., Krefeld, I

Germany Primary ExammerDan|e1 J Fritsch Attorney, Agent, or FirmKarl F. Ross; Herbert 1 Notice: The portion of the term of thls Dubno patent subsequent to Apr. 27, 1988 has been disclaimed.

[22] Filed: Jan. 25, 1971 [57] ABSTRACT A plurality of layers of comminuted material are deposited on an endless conveyor belt, with the uppermost and lowermost layers being finer than the central {63] Continuation-impart of Ser. No. 737,465, June 17, layer or layers. The loosely coherent band thus formed 1968, Pat. No. 3,576,692. is trimmed longitudinally and longitudinally subdivided into a plurality of mats which are fed into a l l 156/382; 156/6 chamber wherein at least one lamina is applied to the 9/ upper surface. This chamber is maintained dust-free [5| [11. Cl. B29j 5/90; B29] 5/08 by pumping filtered air into it so that it is under superi 1 Field of atmospheric pressure. The stacked mat and lamina are 156/557, 570, 517 then fed into a hot press where together they are compressed into a hard coherent laminated pressedboard. [56] References Cited UNITED STATES PATENTS 1,504,218 8/1924 Crowell t 156/381 7 Claims, 5 Drawing Figures 3,017,309 1/1962 Crawford et a1 156/381 A BC I I I 12b 18 22 i i I s.: I3 I20 3 A B C D i 1 a 11 u a l 34 1/ 35 L,F( ,7J s T l" 1 n 11 11 ll 1 J 1 w i 14 f Z i I 1e 4 r--'- SUPER F 2 9 6 ATMOSPHERIC L J PRESSURE SHEET h. u D u m Baa 5 2 22: 5:252 2 83 .62 2 8 852.. A 2

Gerhard H I JTZ INVENTOR.

AT TOR NEY SHEET Ge rha rd HfiTZ INVENTOR.

ATTORNEY z mm 0 HM .w m. w m mm r... E Q 3 Ox N- !i v uiwmnmwwmh B 5&8 w "I on m N 3 r; r \I E 1 N mm m m o. U 1 5 2 m m a u m c 9 m.

mm -L ATTORNEY MTEUTEH JUL 1 SHEET APPARATUS FOR MAKING LAMINATED PRESSED BOARD CROSS-REFERENCE TO (O-PENDING APPLICATION This is a continuation-in-part of my commonly assigned application Ser. No. 737.465 filed .lune I7. I968, now US. Pat. No. 3.576.692.

FIELD OF THE INVENTION My present invention relates to an apparatus for the production of pressed laminates.

BACKGROUND OF THE INVENTION To produce a pressed laminate with a fiber substrate. the customary method is to make a normal coherent fiber or pressed board. to sand and clean it. and then to press laminae onto the finished board in a second pressing operation.

More particularly. the fiberboard is prepared in the manner known in the art. is pressed in a multistage platen press and then is passed to a finishing plant where its surfaces are sanded or polished to prepare it for application of a lamina or of laminae for decorative or protective purposes. The abrasion products are re moved and the lamina or laminae are stacked on this finished fiber-board prior to a second pressing operation in a second multi-platen press.

The finishing operation is expensive and timeconsuming. and the cost of a second multiplaten press greatly contributes to elevating the cost of the final laminated fiberboard. In addition. these later-applied laminae often are not well integrated with the fiberboard core due to the thermosetting qualities of many of the resins used as binders in the commonly known fiber-boards and due to the fact that they cannot bind well to a finished. hard surface.

OBJECT OF THE INVENTION It is an object of my invention to produce an improved pressed laminate more simply than has hitherto been the case.

SUMMARY OF THE INVENTION This object is achieved by applying the laminae to a mat of loosely coherent comminuted material rather than to a finished fiber-board.

In particular. I have found that it is only necessary to prepare a loosely coherent mat of comminuted material upon which the laminate are stacked and/or which is stacked on the laminae prior to the final pressing. l have also found it advantageous to have the original comminutcd material deposited by a plurality of hoppers to form a succession of layers of comminuted matter with finer particles on the top and on the bottom than in the center. the plurality of hoppers also compensating statistically for each other's minor inequalities of feed. thereby producing a very even layer.

This carefully deposited layer is trimmed by means known in the art and subsequently rendered slightly coherent by such means as a single-level or roller press (prcprcss Then it is stacked with one or more laminae according to the desired finished product. and this stack is loaded into a press hose platens are heated during the compression operation.

According to an important feature of this invention. the laminae are stacked on the loosely coherent fiber mat in a dust-free chamber. This prevents endangering the quality of the finished product by airborne dust which would readily adhere to the laminae due to the unavoidable electrostatic forces generated especially when paper. synthetic-resin or metallic foils are used as laminae. It has been found to be impossible to apply a lamina in dusty conditions.

The advantage of doing the major pressing in one operation is that the final pressed laminate is extremely well integrated. all layers being equally well bonded to each other. When two pressing operations are conducted. the fibrous substrate is often imperfectly bonded to the laminations since the surfaces onto which the laminations must bond are hard and unified whereas with my method these surfaces are still somewhat soft thereby providing a better bonding surface for the laminae. Heating the platens ofthe press during the pressing operation also provides a more even bonding.

The platens of the press are formed with a plurality of bores parallel to the pressing surfaces. A heating or cooling fluid is pumped through these bores which are preferably of larger diameter near the center of the platens than near the edges for best heat-exchange re sults DESCRIPTION OF THE DRAWING These features of my invention and others which will become apparent are described below with reference to the drawing in which:

FIG. I is a block diagram illustrating the steps of the process according to my invention;

FIG. 2 is a schematic partial side view of the first stages of a plant for carrying out my method;

FIG. 3 is a view similar to FIG. 2 showing the final stages;

FIG. 4 is a schematic top plan view of a portion of the plant shown in FIGS. 2 and 3; and

FIG. 5 is a sectional side view in enlarged scale of a detail of FIG. 3.

SPECIFIC DESCRIPTION As will be apparent from the drawing, the initial step of the present process (FIG. I) is represented as step A and involves the formation of a continuous layer of comminuted material by hoppers In. lb. and 1d (FIG. 2) located above a conveyor belt 9 driven by a belt 3 whose motor is shown at 3a. These hoppers Ia, lb. l(' and Id may be similar to those of US. Pat. No. 3.224.758.

This layer is subdivided into separate mats. step B. by a slicing mechanism 2 also similar to the one of U.S. Pat. No. 3.224.758.

Before step C. prepressing of the mats. the individual mats pass over a speed-change belt 10 powered by a motor 101! as in the commonly owned US. Pat. No. 3.482.675 of Dec. 9. I969. The prepressing is done by a prepress 5 through which a stainless-steel belt I9 runs powered by a motor 19a. The press 5 is powered by a hydraulic unit 50 which. with the motor 191:. is connected through a control device 5a to a sensor Sh lo cated in the mat level. The press 5 may be that described in commonly owned US. Pat. No. 3.428.505 of Feb. 18. I969.

Step D. trimming of the mats. uses a lateral trimmer 11 (see U.S. Pat. No. 3.224.758) located above a belt 15 driven by a motor 15a. Further downstream of this trimmer 11 is a second sensor connected here to an actuation unit 33 for lifting a section 34 of a belt 35 over a chute 36. A motor 350 drives the belt 35.

The lamination step E, which will be more fully described below. is carried out downstream of the belt 35 after passage of the mats 7 onto a conveyor pallet 13 which can pass them into a high-pressure chamber 12 associated with an air cleansing and pressurizing unit comprising a fan 37 driven by a motor 38 and associated with a filter 41.

The final pressing step F is carried out by a platen press such as that shown in the US. Pat. No. 3.050.777. The press may be fed from a charging rack 16 and discharged onto an unloading rack 17 similar to those in US. Pat. No. 3.379.322.

An integrated pressed laminate is made in the following manner by the above-described plant:

A relatively smooth layer of comminuted or fibrous matter is continuously deposited on the belt-receiving surface formed by the conveyor 9. The hoppers la and 1d are filled with finer comminuted matter than the hoppers 1b and 10 so that the deposited layer is consequently coarser in the middle than at the upper and lower surfaces. Also. because of the use of a plurality of hoppers lala'. the succession of layers gives rise to a band which is quite smooth, any inconsistencies of feed of one hopper being compensated for by the others.

The saw 2 cuts this continuous layer transverse to its direction of travel to form a plurality of incoherent mats. and the spacing between the mats is increased by the speed-change belt 10 (see commonly owned application Ser. No. 702.026 filed Jan, 3]. 1968 by E. Siempelkamp now US. Pat. No. 3.565.725 and entitled PRESSED-BOARD PLANT AND METHOD OF OP- ERATING SAME),

The mats are. one by one. passed onto the conveyor belt 19 running through the press 5. Just before the leading edge ofa mat exits from the press. it triggers the sensor 51) which activates. through the control unit 5a. the unit Sc for closing the press 5 and stopping the belt 19. The mat is quickly pressed. the press 5 opens. and the belt 19 starts moving again to pass it on to the next step.

After pressing. the still loosely coherent mat is trimmed along its longitudinal edges. (i.e. in its direction of travel) by the trimmer 11 as it moves on the belt 15.

On passing under the conventional sensor 32, it is scanned and. when an imperfection is found. the sensor 32 triggers the raising of the section 34 so that the imperfect mat drops into the chute 36.

The mat that is not rejected by the quality control station 32. 33. 34. 36 is passed onto the conveyor tablet 13 (see my application Ser. No. 712.702. now aban doned. which was copending with the parent application Ser. No. 737.465). This entire tablet can move laterally and longitudinally to the direction of travel of its belt to be able to deposit a mat 7 on the conveyor l l running through the high-pressure chamber 12.

The fan 37 sucks air in through the filter 41 so that this chamber 12 is slightly pressurized with dust-free air which exits through the openings 12a I). In this manner the contamination problems caused by the thin laminae are eliminated making for a high-quality end product.

Circulating in and out ofthis chamber 12 through the opening 121) are a plurality of charging plates 18 carried on a conveyor path 22 including the conveyor belt 14. Three vacuum lifters 8a. 8b and 8c move back and forth as shown in FIG. 4 above the conveyor paths and respective stacks of laminae 23 and 6 and laminae 24. These vacuum lifters 8a. 8b and 8c can be raised and lowered over the stacks in conjunction with control of their suction to lift a lamina 23, 24 or 6 or even a charging plate 18 and deposit it in another position. Thus. as one of the charging plates 18 passes along the conveyor path 22, the lifter can deposit a lamina 24 on it. the lifter 8a can deposit another lamina 23 on top of that. the two laminae 23 and 24 being different depending on the finished product desired. Then the conveyor pallet 13 can deposit the prepressed mat 7 on these laminae and the lifter 8a can deposit a lamina 6 on top of that and then another lamina 23. On further passage through the chamber in the direction of an arrow 20, the lifter 8: can drop still another lamina 24 on this stack. thus making a seven-layer laminated board ready for pressing (such as the one shown in FIG. 5). Of course, there may be more or fewer laminae. or they may not be on both sides of the fiber mat according to the programming of the conveyor 22 and the lifters 8a and 8c. The lifter 8!) may be used in case something causes the supply of prepressed mats 7 into the chamber 12 to be interrupted. In this case. it picks the plates 18 up off the conveyor 22 and deposits them in position 48 where they are ready for recirculating when the supply of prepressed mats 7 resumes. Stacking plates may also be used in conjunction with the charging plates 18 for holding of stacks, manufacture of double-thickness boards. or the like.

The laminated board illustrated in FIG. 5 thus com prises a core C formed by an upper layer of relatively fine comminuted material (C'l such as finely divided or powdered sawdust. by one or more intermediate layers C of relatively coarse comminuted material such as wood chips. evploded wood fiber and the like as depos ited frpm the hoppers lb and 1t. and by a final layer C' of finely divided material similar to that formed at C. l have found that because of the use of extremely fine comminuted material such as wood powder for the outer layer C and C special cushioning foils need not be used and high-quality laminates are obtained. ln fact. the quality of such laminates is analogous to those made by the most careful finishing of preformed pressed board by sanding. cleaning or polishing the surfaces of such board prior to the application of laminae thereto. The bond of the foil layer of the instant system. however. is still greater because the synthetic resin or other bonding agent becomes substantially monolithic \\ith the fiber and the superimposed foil in the sy stem of the present invention.

Above the upper layer C of finely divided comminuted material. I may provide a thin foil 6 of a bonding agent. eg. a thermoplastic or thermosetting resin which is represented at B and may be flowable under the heat and pressure of the press. to secure the other laminae '5') the substrate while serving at least in part as a binder tin the layer. A similar bonding layer B may be applied between the layer C"' of finely divided material and the backing foils. A decorative metallic or paper foil D may be bonded by the layer B to the core C while an outer transparent protective layer P (eg. a polyurethane foil) may be simultaneously bonded to the metal or paper foil D. in this case. the upper surface of the board illustrated in FIG. 5 will be that exposed to view. When both surfaces of the board are intended to be seen and must be aesthetically pleasing. a decorative layer D and a protective layer P are used. When the backing surface of the board is not intended for public view. the protective layer P and the decorative layer I) may be replaced by a single-core paper foil. These are the foils constituting the laminae 6. 23 and 24 previously described and discussed in greater detail below.

On leaving the chamber l2, the stack of laminae 23, 24. 6 and mat 7 are loaded onto the charging rack 16 as discussed in the U.S. Pat. No. 3.379.322 or application Ser. No. 702.026. and from thence they are loaded into the platen press 4 resembling that of the US Pat. No. 3.050.777. The discharging rack i7 is also constructed as described in US. Pat. No. 3.379.322. Here. however. the plate 18 is fed into the press along with the laminate. After pressing. the pressed iaminate is separated from the plate 18 and the plate is recirculated as represented at 22 while the finished laminate is further trimmed or just stacked awaiting delivery.

In order to attain a high-quality pressed laminate with well integrated laminae, the press 4, according to my invention. is constructed as shown in FIG. 5. The platens 25 are separated by spacers which make for a finished pressed laminate with parallel surfaces. This eliminates many of the problems often caused by un equal closing or abutting platens. problems which have proved especially troublesome in lamination systems. in addition. a heating and cooling arrangement is pro vided for the press e. The platens 25 of the press 4 are formed with a multitude of bores 26. 27 and 28 throughout them. These boxes are provided at their ends with manifolds 50 and 51 and are here connected through a pump 44 and two valves 42 and 43 to two reservoirs 45 and 46 containing. respectively. a heated and cooled liquid. These valves 42, 43 are controlled by a switch 47 that is actuated on the closing of the platens 25 to connect the bores 26. 27 and 28 up to the hot-liquid reservoir 45 and the pump 44 and. in an open condition of the platens 25, to the cold liquid reservoir 46.

Instead of the spacer strips 30, presses such as disclosed in U.S. Pat. Nos. l.3l8.794. 2.586.474. 2.792.777, 2,913,027. 3.361.056. 2.172.003. 2.884.032. or German Offenlegungsschrift 1.807.433 are usable. These patents disclose presses wherein the spacing between the separate platens is controlled automatically by lever arrangements. It is also known to use stepped pulleys to control platen spacing.

In this manner the platens 25 are cool or being cooled whenever they are opened. that is. whenever they are being loaded or unloaded. However. they heat when closed to integrate the laminations being pressed between them. This eliminates the possibility of heating one lamina more than another. since the heating only sets in upon closing ofthe press 4. all platens 25 being cooled or at least relatively chilled during loading. In addition. the cooling subsequent to heating makes for a pressed laminate which. on removal from the press 4. in stiff. not still hot and somewhat pliable. This also circumvents the necessity of extra careful unloading. since the chilled pressed laminates are reasonably durabic.

The development ofthermosetting binders which set after a predetermined interval has made it possible to eliminate the cooldown feature discussed above. When such binders are used. it is only important that the board which remains in the press the longest. i.e. the first loaded board. not stay in the press prior to pressing long enough for its binder to set. ln this manner. all of the boards will have their binders melted and will be pressed. with their setting times being different. The finished products are. however. identical.

For best effect the bores 26-28 near the edge of the platen 25 have a diameter D of some 30mm in a platen 25 of a thickness of lOOmm or greater. with a space A between them of around 5mm. This diameter D becomes a slightly larger diameter D toward the center of the platen 25 while the space A becomes a correspondingly smaller space A. In this manner a most effective heat-exchange medium to platen-cubic-volume ratio is attained. and the platens 25 are most quickly heated with a minimum of energy loss while not appreciably losing mechanical strength.

The charging plates 18 can be dispensed with altogether. especially if a charging pack 16 such as the one of commonly owned U.S. Pat. No. 3.428.505 is used.

The improvement described and illustrated is believed to admit of many modification within the ability of persons skilled in the art. all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.

I claim:

1. An apparatus for producing pressed board comprising:

means for forming a loosely coherent mat of comminuted material;

means for applying at least one lamina to said loosely coherent mat in a lamination zone; means for excluding dust from said zone by maintaining same under superatmospheric pressure;

means for thereafter hot-pressing said loosely coherent mat and the lamina superposed thereon together between two pressing surfaces to render the mat coherent and simultaneously bond said lamina thereto;

means for continuously depositing a first layer of relatively fine comminuted material;

means for continuously depositing a second layer of relatively coarse comminuted material on said first layer;

means for continuously depositing a third layer of relatively fine comminuted material on said second layer; and

means for longitudinally subdividing the superposed continuous layers into individual mats. said lamina being applied to one of said layers of relatively fine material.

2. An apparatus for the production of laminated pressed board. said apparatus comprising:

conveyor means forming an advancing receiving surface defining a transport direction:

dispensing means above said surface for depositing thereon a mass of comminuted material in a substantially continuous band;

mat-forming means adjacent said surface downstream of said dispensing means for longitudinally subdividing said band into a plurality of individual loosely coherent mats;

means forming a substantially closed chamber downstream of said mat-forming means;

transparent means for passing said mats through said chamber;

stacking means in said chamber for applying at least one lamina to each of said mats;

means for maintaining superatmospheric pressure in said chamber and thereby excluding dust from said chamber; and

a heated platen press downstream of said chamber for hot pressing each loosely coherent mat with its respective lamina into a hard coherent laminated pressed board 3. The apparatus defined in claim 2 wherein said means for excluding dust from said chamber includes an intake fan and a dust filter, said intake fan adapted to draw air into said chamber through said filter.

4. The apparatus defined in claim 2 wherein said dispensing means includes a first dispenser for dispensing a first layer of relatively fine comminuted material on said surface. a second dispenser downstream of said first dispenser for dispensing a second layer of relatively coarse comminuted material on said first layer. and a third dispenser downstream of said second dispenser for dispensing a third layer of relatively fine comminuted material on said second layer.

5. The apparatus defined in claim 4 wherein each of said dispensers is a hopper said conveyor means including an endless transport hand forming said surface.

6. The apparatus defined in claim 5 wherein said press includes a pair of platens displaceable toward each other and means for heating said platens.

7. The apparatus defined in claim 2 wherein said stacking means includes at least one vertically displaceable vacuum lifter displaceable transverse to said transport direction in said chamber to lift a lamina from a stack thereofin said chamber and place same on a mat in said chamber. 

1. AN APPARATUS FOR PRODUCING PRESSED BOARD COMPRISING: MEANS FOR FORMING A LOOSELY COHERENT MAT OF COMMINUTED MATERIAL, MEANS FOR APPLYING AT LEAST ONE LAMINA TO SAID LOOSELY COHERENT MAT IN A LAMINATION ZONE, MEANS FOR EXCLUDING DUST FROM SAID ZONE BY MAINTAINING SAMD UNDER SUPERATMOSPHERIC PRESSURE, MEANS FOR THEREAFTER HOT-PRESSING SAID LOOSELY COHERENT MAT AND THE LAMINA SUPERPOSED THEREON TOGETHER BETWEEN TWO PRESSING SURFACES TO RENDER THE MAT COHERENT AND SIMULTANEOUSLY BOND SAID LAMINA THERETO, MEANS FOR CONTINUOUSLY DEPOSITING A FIRST LAYER OF RELATIVELY FINE COMMINUTED MATERIAL, MEANS FOR CONTINUOUSLY DEPOSITING A SECOND LAYER OF RELATIVELY COARSE COMMINUTED MATERIAL ON SAID FIRST LAYER, MEANS FOR CONTINUOUSLY DEPOSITING A THIRD LAYER OF RELATIVELY FINE COMMINUTED MATERIAL ON SAID SECOND LAYER, AND MEANS FOR LONGITUDINALLY SUBDIVIDING THE SUPERPOSED CONTINUOUS LAYERS INTO INDIVIDUAL MATS, SAID LAMINA BEING APPLIED TO ONE OF SAID LAYERS OF RELATIVELY FINE MATERIAL.
 2. An apparatus for the production of laminated pressed board, said apparatus comprising: conveyor means forming an advancing receiving surface defining a transport direction; dispensing means above said surface for depositing thereon a mass of comminuted material in a substantially continuous band; mat-forming means adjacent said surface downstream of said dispensing means for longitudinally subdividing said band into a plurality of individual loosely coherent mats; means forming a substantially closed chamber downstream of said mat-forming means; transparent means for passing said mats through said chamber; stacking means in said chamber for applying at least one lamina to each of said mats; means for maintaining superatmospheric pressure in said chamber and thereby excluding dust from said chamber; and a heated platen press downstream of said chamber for hot pressing each loosely coherent mat with its respective lamina into a hard coherent laminated pressed board.
 3. The apparatus defined in claim 2 wherein said means for excluding dust from said chamber includes an intake fan and a dust filter, said intake fan adapted to draw air into said chamber through said filter.
 4. The apparatus defined in claim 2 wherein said dispensing means includes a first dispenser for dispensing a first layer of relatively fine comminuted material on said surface, a second dispenser downstream of said first dispenser for dispensing a second layer of relatively coarse comminuted material on said first layer, and a third dispenser downstream of said second dispenser for dispensing a third layer of relatively fine comminuted material on said second layer.
 5. The apparatus defined in claim 4 wherein each of said dispensers is a hopper, said conveyor means including an endless transport band forming said surface.
 6. The apparatus defined in claim 5 wherein said press includes a pair of platens displaceable toward each other and means for heating said platens.
 7. The apparatus defined in claim 2 wherein said stacking means includes at least one vertically displaceable vacuum lifter displaceable transverse to said transport direction in said chamber to lift a lamina from a stack thereof in said chamber and place same on a mat in said chamber. 